Referring now to FIG. 1, an exemplary magnetic storage system 10 such as a hard disk drive is shown. A buffer 14 stores data that is associated with the control of the hard disk drive and/or buffers data to optimize block sizes for increased transfer speed. The buffer 14 may employ SDRAM or other types of low latency memory. A processor 16 performs processing that is related to the operation of the hard disk drive. A hard disk controller (HDC) 18 communicates with the buffer 14, the processor 16, a spindle/voice coil motor (VCM) driver 20, and/or a read/write channel circuit 24. A host 26 sends data read/write requests to the HDC 18.
During a write operation, the read/write channel circuit (or read channel circuit) 24 encodes the data to be written onto the storage medium. The read/write channel circuit 24 processes the signal for reliability and may include, for example error correction coding (ECC), run length limited coding (RLL), and the like. During read operations, the read/write channel circuit 24 converts an analog output from the medium to a digital signal. The converted signal is then detected and decoded by known techniques to recover the data written on the hard disk drive.
One or more platters 28 include a magnetic coating that stores magnetic fields. The platters 28 are rotated by a spindle motor that is schematically shown at 30. Generally the spindle motor 30 rotates the platter 28 at a fixed speed during the read/write operations. One or more read/write arms 34 move relative to the platters 28 to read and/or write data to/from the platters 28. The spindle/VCM driver 20 controls the spindle motor 30, which rotates the platter 28. The spindle/VCM driver 20 also generates control signals that position the read/write arm 34, for example using a voice coil actuator, a stepper motor or any other suitable actuator.
A read/write device 36 is located near a distal end of the read/write arm 34. The read/write device 36 includes a write element such as an inductor that generates a magnetic field. The read/write device 36 also includes a read element (such as a magneto-resistive (MR) sensor) that senses the magnetic fields on the platter 28. A preamplifier (preamp) 40 amplifies analog read/write signals. When reading data, the preamp 40 amplifies low level signals from the read element and outputs the amplified signal to the read/write channel circuit 24. The preamp 40 may include a high pass amplifier. While writing data, a write current that flows through the write element of the read/write channel circuit 24 is switched to produce a magnetic field having a positive or negative polarity. The positive or negative polarity is stored by the platter 28 and is used to represent data.
Referring now to FIG. 2, the read/write channel circuit 24 outputs write signals wdx and wdy to the preamp 40 when writing data. The preamp 40 amplifies the write signals using a write amplifier 42. The amplified write signals are output to the read/write device 36. When reading data, the preamp 40 receives signals from the read/write device 36, amplifies the signals using a read amplifier 44, and outputs amplified read signals rdx and rdy to the read/write channel circuit 24. Other types of the read elements of the read/write device 36 include tunneling magneto-resistive (TMR) and giant magneto-resistive (GMR) sensors.